It is not true that my book “Guns, Germs and Steel,” as Mr. Romneydescribed it in a speech in Jerusalem, “basically says the physical characteristics of the land account for the differences in the success of the people that live there. There is iron ore on the land and so forth.”

That is so different from what my book actually says that I have to doubt whether Mr. Romney read it. My focus was mostly on biological features, like plant and animal species, and among physical characteristics, the ones I mentioned were continents’ sizes and shapes and relative isolation. I said nothing about iron ore, which is so widespread that its distribution has had little effect on the different successes of different peoples. (As I learned this week, Mr. Romney also mischaracterized my book in his memoir, “No Apology: Believe in America.”)

That’s not the worst part. Even scholars who emphasize social rather than geographic explanations — like the Harvard economist David S. Landes, whose book “The Wealth and Poverty of Nations” was mentioned favorably by Mr. Romney — would find Mr. Romney’s statement that “culture makes all the difference” dangerously out of date. In fact, Mr. Landes analyzed multiple factors (including climate) in explaining why the industrial revolution first occurred in Europe and not elsewhere.